Sensor offers cheaper, more accurate way to detect drunk drivers

Although colour change-based devices aren't exactly new, the researchers claim their sensor is the first to provide a precise digital readout. The breathalyser is also reusable, and can detect alcohol at much higher concentrations compared to other portable devices. "Our approach enables an optical, naked-eye detection as a colour change from green to red, like litmus paper," said Riccardo Pernice, of the Università degli Studi di Palermo. "But it also potentially permits accurate quantitative measurements with the addition of an electronic system or a colour detector." The design makes use of the sensing properties of opals, a type of gemstone, to detect the gas version of ethanol. To start, the researchers created sheets of manufactured opal about 1cm² and just a few hundred billionths of a meter thick. The opals were pumped full of a gel tuned to respond to ethanol vapour. At increasing ethanol concentrations, the gel swells, changing the way light travels through the opal and causing the sample to become red. In tests, the researchers found that the sample gradually regained its original colour after less than one minute of exposure in air. They are now working towards a commercial prototype.